1. Field of the Invention
The present invention relates to a liquid crystal display device of a transverse electric field driving mode, and a method of manufacturing a pixel electrode which is applied to this liquid crystal display device.
2. Description of the Related Art
In recent years, flat-panel display devices have vigorously been developed, and liquid crystal display devices, above all, have attracted attention because of advantages of light weight, small thickness and low power consumption. In particular, in an active matrix liquid crystal display device in which a switching element is provided in each of pixels, attention has been paid to the structure which makes use of a transverse electric field (including a fringe electric field) of an in-plane switching (IPS) mode or a fringe field switching (FFS) mode (see, for instance, Jpn. Pat. Appln. KOKAI Publication No. 2005-107535 and Jpn. Pat. Appln. KOKAI Publication No. 2006-139295).
The liquid crystal display device of such a transverse electric field driving mode includes a pixel electrode and a counter-electrode which are formed on an array substrate and are opposed via an interlayer insulation film, and liquid crystal molecules are switched by generating a transverse electric field that is substantially parallel to the major surface of the array substrate. In addition, polarizer plates, which are disposed such that their absorption axes intersect at right angles, are disposed on the outer surfaces of the array substrate and the counter-substrate.
By this disposition of the polarizer plates, the display of a black screen is realized, for example, at a time of non-application of voltage. With the application of a voltage corresponding to a video signal to the pixel electrode, the transmittance (modulation ratio) gradually increases and the display of a white screen is realized. In this liquid crystal display device, the liquid crystal molecules rotate in a plane that is substantially parallel to the major surface of the substrate. Thus, since the polarization state is not greatly affected by the direction of incidence of transmissive light, there is the feature that the viewing angle dependency is low and a wide viewing angle characteristic is obtained.
In particular, in the FFS mode liquid crystal display device, the pixel electrode is disposed to be opposed to a counter-electrode via an interlayer insulation film. The pixel electrode has a slit which is opposed to the counter-electrode. The liquid crystal molecules are driven by an electric field which is generated between the pixel electrode and the counter-electrode via the slit.
In the pixel electrode having this shape, there may be a case in which the directions of electric fields are not uniform in the vicinity of both end portions of the slit. Hence, in the vicinity of both end portions of the slit, the directions of alignment of liquid crystal molecules, which are driven by electric fields in non-uniform directions, also become non-uniform. Specifically, at a time of voltage application (at a time of white screen display), an alignment defect of liquid crystal molecules occurs in the vicinity of both end portions of the slit, and the transmittance in this part (domain) lowers, resulting in a dark line. There is a tendency that the domain in which such an alignment defect has occurred grows along the edges of the slit, and a further decrease in transmittance may occur. Thus, there is such a problem that an adequately high luminance cannot be obtained when a white screen is displayed.